getInstance(String algorithm)
java.security.KeyPairGenerator类的getInstance()方法用于返回KeyPairGenerator对象,该对象为指定算法生成公用/专用 key 对。
此方法从最喜欢的提供者开始遍历已注册的安全提供者列表。返回一个新的KeyPairGenerator对象,该对象封装了支持指定算法的第一个Provider的KeyPairGeneratorSpi实现。
用法:
public static KeyPairGenerator getInstance(String algorithm) throws NoSuchAlgorithmException
参数:此方法将“算法”的标准名称作为参数。
返回值:此方法返回新的KeyPairGenerator对象。
异常:如果没有提供者支持指定算法的Signature实现,则此方法将引发NoSuchAlgorithmException。
下面是说明getInstance()方法的示例:
示例1:
// Java program to demonstrate
// getInstance() method
import java.security.*;
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
{
try {
// creating the object of
// KeyPairGenerator
// and getting instance
// using getInstance() method
KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA");
// getting the Algorithm
String algo = sr.getAlgorithm();
// printing the algo String
System.out.println("Algorithm : " + algo);
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (ProviderException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Algorithm : DSA
示例2:显示NoSuchAlgorithmException
// Java program to demonstrate
// getInstance() method
import java.security.*;
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
{
try {
// creating the object of
// KeyPairGenerator
// and getting instance
// using getInstance() method
System.out.println("Trying to get"
+ " the instance of unknown Algorithm");
KeyPairGenerator sr = KeyPairGenerator
.getInstance("TAJMAHAL");
// getting the Algorithm
String algo = sr.getAlgorithm();
// printing the algo String
System.out.println("Algorithm : " + algo);
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (ProviderException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Trying to get the instance of unknown Algorithm Exception thrown : java.security.NoSuchAlgorithmException: TAJMAHAL KeyPairGenerator not available
getInstance(String algorithm, Provider provider)
java.security.KeyPairGenerator类的getInstance()方法用于返回KeyPairGenerator对象,该对象为指定算法生成公用/专用 key 对。
返回一个新的KeyPairGenerator对象,该对象封装了来自指定Provider对象的KeyPairGeneratorSpi实现。请注意,指定的提供程序对象不必在提供程序列表中注册。
用法:
public static KeyPairGenerator getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
参数:此方法将以下参数作为参数:
- algorithm:请求的算法的名称。
- provider:提供者
返回值:此方法返回新的KeyPairGenerator对象。
异常:此方法引发以下异常:
- NoSuchAlgorithmException –如果指定的Provider对象不提供指定算法的SignatureSpi实现。
- IllegalArgumentException –如果提供者为null。
下面是说明getInstance()方法的示例:
注意:以下程序将无法在在线IDE上运行。
示例1:
// Java program to demonstrate
// getInstance() method
import java.security.*;
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
{
try {
// creating the object of
// KeyPairGenerator
// and getting instance
// using getInstance() method
KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA");
// creating Provider object
Provider pd = sr.getProvider();
// getting algorithm name
// by using getAlgorithm() mathod
String algo = sr.getAlgorithm();
// creating the object of KeyPairGenerator and getting instance
// By usng getInstance() method
KeyPairGenerator sr1 = KeyPairGenerator.getInstance(algo, pd);
// getting the status of signature object
KeyPair keypair = sr1.generateKeyPair();
// printing the keypair
System.out.println("Keypair : " + keypair);
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (ProviderException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Keypair : java.security.KeyPair@12a3a380
示例2:显示NoSuchAlgorithmException
// Java program to demonstrate
// getInstance() method
import java.security.*;
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
{
try {
// creating the object of
// KeyPairGenerator
// and getting instance
// using getInstance() method
KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA");
// creating Provider object
Provider pd = sr.getProvider();
// creating the object of KeyPairGenerator and getting instance
// By usng getInstance() method
KeyPairGenerator sr1 = KeyPairGenerator.getInstance("TAJMAHAL", pd);
// getting the status of signature object
KeyPair keypair = sr1.generateKeyPair();
// printing the keypair
System.out.println("Keypair : " + keypair);
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (ProviderException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Exception thrown : java.security.NoSuchAlgorithmException: no such algorithm: TAJMAHAL for provider SUN
示例3:显示IllegalArgumentException
// Java program to demonstrate
// getInstance() method
import java.security.*;
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
{
try {
// creating the object of
// KeyPairGenerator
// and getting instance
// using getInstance() method
KeyPairGenerator sr = KeyPairGenerator
.getInstance("RSA");
// creating Provider object
System.out.println("Trying to assign null as a provider");
Provider pd = null;
// getting algorithm name
// by using getAlgorithm() mathod
String algo = sr.getAlgorithm();
// creating the object of KeyPairGenerator and getting instance
// By usng getInstance() method
KeyPairGenerator sr1 = KeyPairGenerator
.getInstance(algo, pd);
// getting the status of signature object
KeyPair keypair = sr1.generateKeyPair();
// printing the keypair
System.out.println("Keypair : " + keypair);
}
catch (NoSuchAlgorithmException e) {
System.out.println("Exception thrown : " + e);
}
catch (ProviderException e) {
System.out.println("Exception thrown : " + e);
}
catch (IllegalArgumentException e) {
System.out.println("Exception thrown : " + e);
}
}
}
Trying to assign null as a provider Exception thrown : java.lang.IllegalArgumentException: missing provider
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注:本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 KeyPairGenerator getInstance() method in Java with Examples。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。